Mercury is often contained as a minor constituent in mineral concentrates and is an undesirable metal in the treatment of such concentrates for the recovery of the desired mineral values. In various recovery processes, mercury tends to accumulate in intermediate metallurgical materials in certain process steps, as well as in off-gases and effluents from which the mercury is often removed in the form of mercury-containing material, such as wastes, residues, sludges, precipitates and the like. Similar mercury-containing material may be formed in the chemical process industry. This mercury-containing material can not be discarded, and must either be carefully stored or converted into a usable form. The mercury-containing material generally contains mercury in the form of mercurous and/or mercuric salts such as the chlorides, sulfates or nitrates. The conversion of these salts into a usable form could be accomplished by a reduction with the formation of elemental mercury.